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Investigation and characterization of the modifying action of bioactive components on the enzymatic activity of the human aldehyde dehydrogenase ALDH3A1 (Master thesis)

Κρασά, Φλωρεντία/ Kasa, Florentia

The beneficial properties and benefits of natural substances and essential oils have been known since ancient times. The objective of this study was to evaluate the effect of various phytochemicals and essential oils on the enzymatic activity of aldehyde dehydrogenase 3A1. Human aldehyde dehydrogenase 3A1 (hALDH3A1) or hsALDH3A1 (as indicated) is the major isoform of the superfamily of aldehyde dehydrogenases (hALDHs) in saliva, esophagus, stomach, bladder, cornea, lungs and skin. hALDH3A1's main function is the oxidation of toxic endogenous and exogenous medium-length aliphatic and aromatic aldehydes to their corresponding non-toxic carboxylic acids, using NAD+ as a cofactor. Those aldehydes can be obtained either from the environment, alcohol, smoking, even from the consumption of junk foods etc. Specific substrates of hALDH3A1 are medium-sized aldehydes consisted of over 6 carbons, such as benzaldehyde, cinnamic aldehyde and 2-naphthaldehydes. Except for its specific substrates, hALDH3A1 can also oxidize acetaldehyde to a much lesser extent. hALDH3A1 has structural properties as a corneal crystallin, often functions as an esterase, and recent studies suggest that it also exhibits chaperone-like activity. Due to its expression in tissues which are main entrances to the human body, hALDH3A1 could be actively participate in the first line of defense. Besides that, treatment of head and neck cancers with chemotherapy reduces the activity of hALDH3A1, causing dry mouth and other unpleasant effects. So, finding substances with a modifying action on hALDH3A1's activity could be an important ally in avoiding these side effects. In this work we studied the effect of 15 phytochemicals on the dehydrogenase activity of hALDH3A1 against benzaldehyde and acetaldehyde. In addition, the effect of all substances on the esterase activity of hALDH3A1 with para-nitrophenyl acetate (p-NPA) as substrate was tested. Our results showed that the presence of these substances did not affect the dehydrogenase activity of hALDH3A1 against benzaldehyde. On the other hand, the presence of Citral, Kumquat, Aloysia and Limonene increased the dehydrogenase activity of the protein against acetaldehyde while the presence of Mentha and Carvone decreased it. In addition, the esterase activity of hALDH3A1 was decreased in the presence of 5 of the essential oils tested. Moreover, preliminary crystallization experiments have been conducted with final aim the determination of the 3D structures of the complexes by X-ray crystallography.